747
FXUS66 KPDT 250931
AFDPDT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE PENDLETON OR
231 AM PDT FRI SEP 25 2026
KEY MESSAGES
- WIDESPREAD RAIN SHOWERS AND BREEZY TO WINDY CONDITIONS WILL
DEVELOP THROUGHOUT TODAY, WITH AN ISOLATED THUNDERSTORM OR TWO
IN THE WASHINGTON CASCADES
- WIND ADVISORIES IN EFFECT TODAY FROM CENTRAL OREGON TO THE
LOWER COLUMBIA BASIN
- DRY CONDITIONS AND LIGHT WINDS RETURN OVER THE WEEKEND, THEN A
RETURN OF PERIODIC LIGHT SHOWERS IN THE CASCADES NEXT WEEK
DISCUSSION
SATELLITE AND RADAR IMAGERY TONIGHT SHOW A SURFACE
LOW AND UPPER TROUGH SWINGING INTO THE PACNW, WITH A COLD FRONT
PUSHING A BAND OF RAIN ACROSS THE CASCADE EAST SLOPES.
TODAY THROUGH SUNDAY: THE NORTH/SOUTH ORIENTED BAND OF RAIN
LEADING THE COLD FRONT AND SURFACE LOW WILL CONTINUE TO PUSH
EAST THIS MORNING AND EXIT IN THE AFTERNOON. POST FRONTAL
SHOWERS WILL CONTINUE ACROSS THE CASCADE CREST AND EAST SLOPES
THANKS TO SUPPORT FROM THE UPPER TROUGH PASSAGE, BUT WILL
DIMINISH THROUGH THE EVENING HOURS AS THE TROUGH EXITS TO THE
NORTHEAST. THERE REMAINS A WIDESPREAD 60-90% CHANCE OF AT LEAST
MEASURABLE RAIN ACROSS MUCH OF THE FORECAST AREA TODAY, WITH
ONLY A 30-45% CHANCE OF 0.25 INCHES IN THE NORTHERN BLUES AND A
65-95% CHANCE OF 0.5 INCHES ALONG THE CASCADE CREST AND EAST
SLOPES. IN ADDITION TO PRECIPITATION, THE UPPER TROUGH AND
SURFACE LOW PASSAGE WILL BRING INCREASING WEST TO SOUTHWEST
WINDS ACROSS THE FORECAST AREA. WINDS WILL BE 25-35 MPH WITH
GUSTS 35-50 MPH THROUGH THE CASCADE GAPS, CENTRAL OR, AND INTO
THE COLUMBIA BASIN AND ADJACENT FOOTHILLS/VALLEYS. WINDS 15-25
MPH AND GUSTS UP TO 35 MPH ARE EXPECTED IN MOST OTHER LOCATIONS,
WITH STRONGER WINDS ALONG THE CASCADE CREST. SURFACE WINDS WILL
BE SUPPORTED BY A 40-50KT LOW LEVEL JET THAT WILL MIX DOWN
ACROSS PORTIONS OF THE COLUMBIA BASIN THIS AFTERNOON. WIND
ADVISORIES ARE IN EFFECT ACROSS CENTRAL/NORTH CENTRAL OR,
COLUMBIA BASIN/GORGE, YAKIMA VALLEY, AND THE BLUE MOUNTAIN
FOOTHILLS FROM 8AM TO 11PM TODAY.
SHOWER ACTIVITY AND WINDY CONDITIONS WILL DIMINISH TONIGHT INTO
SATURDAY AS THE UPPER TROUGH AND SURFACE LOW EXIT TO THE
NORTHEAST. DETERMINISTIC AND ENSEMBLE GUIDANCE CONTINUE TO
DEPICT WEAK BROAD TROUGHING DEVELOPING OFFSHORE THE PACNW
SATURDAY, THEN SLIDING ACROSS THE REGION THROUGH SUNDAY. THE
TROUGH PASSAGE WILL LACK MOISTURE AND MID TO UPPER LEVEL JET
SUPPORT, RESULTING IN DRY CONDITIONS WITH LIGHT WINDS. IT WILL
HOWEVER CONTINUE TO SUPPORT BELOW NORMAL TEMPERATURES ACROSS THE
REGION, WITH AFTERNOON HIGHS IN THE 60S. WHILE WIDESPREAD
OVERNIGHT FREEZING TEMPERATURES (OUTSIDE OF THE MOUNTAIN ZONES)
ARE NOT EXPECTED TO DEVELOP, AREAS OF THE WALLOWA VALLEY AND
CENTRAL OR WILL SEE A 25-65% CHANCE OF FREEZING MORNING
TEMPERATURES SATURDAY. THE MAKE OR BREAK FOR FREEZING
TEMPERATURES WILL BE CLOUD COVER IN THE OVERNIGHT AND EARLY
MORNING HOURS, THOUGH CONFIDENCE IS LOW (25-35%) IN EXTENT OF
CLOUD COVER FOR TOMORROW MORNING.
MONDAY THROUGH THURSDAY: ENSEMBLE GUIDANCE IS IN GOOD AGREEMENT
OF MOSTLY ZONAL FLOW DEVELOPING OVER THE PACNW AS AN UPPER
TROUGH DEVELOPS OVER AK AND NORTHERN BC AND RIDGING OUT IN THE
EASTERN PACIFIC THROUGH TUESDAY. WHILE MONDAY WILL REMAIN MOSTLY
DRY, ENSEMBLE CLUSTER SOLUTIONS HINT AT A SHORTWAVE AND
ATTENDANT WEAK FRONTAL PASSAGE BRINGING LIGHT RAIN SHOWERS TO
THE CASCADE CREST AND EAST SLOPES THROUGHOUT TUESDAY, THOUGH
ABOUT 30-45% OF CLUSTER MEMBERS BRING LIGHT RAIN TO THE NORTHERN
BLUES LATTER HALF OF TUESDAY. WINDS ARE FAVORED TO REMAIN LIGHT
TO LOCALLY BREEZY WITH THE SYSTEM PASSAGE TUESDAY (CONFIDENCE
60-65%).
DISAGREEMENT GROWS AMONGST ENSEMBLE MEMBERS MID WEEK IN THE
EVOLUTION OF THE SYNOPTIC PATTERN. SOLUTIONS RANGE FROM RIDGING
WEDNESDAY THEN UPPER TROUGH PASSAGE THURSDAY TO SLOW MOVING
TROUGHING WEDNESDAY INTO THURSDAY. EITHER SOLUTIONS WOULD FAVOR
MORE MOUNTAIN PRECIPITATION, BUT WITH PLENTY OF DISAGREEMENT
AMONGST THE MEMBERS, CONFIDENCE IS LOW (20-25%) IN EXTENT,
TIMING, AND AMOUNTS OF PRECIPITATION NEXT WEEK.
AVIATION /06Z TAFS THROUGH 06Z SATURDAY/
VFR CONDITIONS ARE
FORECAST THROUGH THE PERIOD. WHILE THEY CANNOT BE ENTIRELY RULED
OUT, CONFIDENCE IN MVFR CIGS/VSBYS IS LOW (20% OR LESS) AT ALL
SITES.
A LOW-PRESSURE SYSTEM WILL BRING RAIN AND RAIN SHOWERS TO THE
REGION OVERNIGHT INTO FRIDAY MORNING, WITH SOME LOW (10-30%)
CHANCES OF LINGERING POST-FRONTAL RAIN SHOWERS THROUGH THE
AFTERNOON.
WINDS WILL BECOME BREEZY TO VERY WINDY AT ALL SITES, GENERALLY
15-25 KTS WITH GUSTS OF 25-35 KTS, BY MIDDLE TO LATE MORNING.
PRELIMINARY POINT TEMPS/POPS
PDT 69 40 65 41 / 90 0 0 0
ALW 69 45 66 44 / 90 10 0 0
PSC 72 43 69 41 / 70 0 0 0
YKM 65 40 64 40 / 30 0 0 0
HRI 72 43 68 40 / 80 0 0 0
ELN 61 36 60 36 / 50 10 0 0
RDM 59 31 64 33 / 10 0 0 0
LGD 66 38 64 38 / 60 0 0 0
GCD 66 37 67 40 / 50 0 0 0
DLS 66 45 68 45 / 60 10 0 0
PDT WATCHES/WARNINGS/ADVISORIES
WA...WIND ADVISORY FROM 8 AM THIS MORNING TO 11 PM PDT THIS EVENING
FOR WAZ024-027-521.
WIND ADVISORY FROM 11 AM THIS MORNING TO 11 PM PDT THIS
EVENING FOR WAZ028-029.
OR...WIND ADVISORY FROM 8 AM THIS MORNING TO 11 PM PDT THIS EVENING
FOR ORZ041-044-507-508-510.
WIND ADVISORY FROM 8 AM THIS MORNING TO 5 PM PDT THIS
AFTERNOON FOR ORZ511.
DISCUSSION...82
AVIATION...86
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